The invention relates to an arrangement for a telescope feeder of a rock-drilling machine, a feed beam of which feeder consists of two telescopic portions moving mutually in their longitudinal direction, between which portions is connected an extension cylinder, inside which moves a piston in such a way that the extension cylinder is connected to one telescopic portion and the piston rod is connected to the other telescopic portion in order to displace those portions with respect to each other, whereby the rock-drilling machine moves along one telescopic portion by means of a separate feed cylinder.
Telescope feeders are used in a rock-drilling machine in a situation when it is necessary to drill holes of different lengths in different circumstances, owing to which a long feed beam cannot always be used. In such a telescope feeder, the feed beam consists of two feed beam portions moving in their longitudinal direction with respect to each other, whereby for drilling with the shortest drill rod is only needed a motion of the drilling machine with respect to one feed beam portion, but for drilling with drill rods longer than that the feed motion consists both of the motion of the drilling machine along one feed beam portion and of a mutual motion of the feed beam portions.
One problem with the known solutions is that when the feed beam portions are displaced with respect to each other, their position cannot be accurately determined without complicated measuring devices. A consequence of this is that the feed motion is difficult to control and it causes extra work and inconveniences. On the other hand, for drilling holes of predetermined lengths a continuous measurement of drill rod motion is required, which also is difficult and demands a continuous observation on the part of the driller.
The object of the present invention is to provide such an arrangement for a telescope feed beam of a rock-drilling machine by which the feed length can be easily arranged as desired and locked thereto in such a way that no measuring steps are necessary after the first setting before the length of the drill rod or the depth of the hole to be drilled is changed. The arrangement according to the invention is characterized in that the extension cylinder comprises separate adjusting piston mounted movably around the piston rod so that it can move irrespective of the piston of the extension cylinder, whereby three separate cylinder spaces are formed inside the extension cylinder, and that to each cylinder space is connected a separate channel for pressure medium, whereby the adjusting piston can be displaced to a desired position with respect to the extension cylinder or the piston and it can be locked thereto.
The essential idea of the invention is that the extension cylinder between the feed beam portions comprises a separate adjusting piston, which can move around the piston rod of the cylinder in the longitudinal direction of the cylinder, whereby three spaces for pressure medium are formed in the cylinder and whereby the flow of pressure fluid into one of these spaces or out of it can be closed in such a way that the adjusting piston restricts the stroke length of the piston of the extension cylinder to a desired dimension. In this manner it is possible to adjust the length of motion between the beam portions of the telescope feed beam in such a way that the desired drilling length is achieved.
The invention will be described in more detail below in connection with the attached drawings.